In the surgical treatment of peptic ulcers, selective parietal cell vagotomy offers an approach to the elimination of neurogenic control of acid secretion without the need for a total vagotomy or a drainage procedure. Studies will be undertaken in dogs to assess the contractile parameters of the antral duodenal area following a parietal cell vagotomy (PCV) or a truncal vagotomy (TV). These will be challenged with a citrate test meal, a citrate-fat test meal, bethanechol and insulin. Following this study, a Heineke-Mikulicz pyloroplasty will be performed and the various challenges repeated. Another study will evaluate the role of the gastroduodenal junction (hypomuscular segment) in the coordination of the antrum and duodenum. We will monitor the mechanical (4 dogs) and electrical (4 dogs) activity in the junctional area following the ablation of the hypomuscular segment of the anterior surface. These latter experiments will assess whether mechanical or electrical activity can propogate across the normal or surgically altered gastroduodenal junction.